NBC's breakout hit returns for a new episode on Tuesday after taking a week off for the election, and fans of the show will get to see the Pearson family taking on the '90s. ET was with Mandy Moore and Milo Ventimiglia on the set of This Is Us in late September when they were filming the installment.

"I'm in my 40s and you're almost 50," Moore, who plays Rebecca, said of her character's older age, before referencing her onscreen husband, Jack.

Moore and Ventimiglia, sporting a goatee, were dressed in their best '90s sleepwear for a bedroom scene. But for fans of Rebecca and Jack, don't think that things are going swimmingly for the beloved TV couple.

"The relationship is not in the greatest place," the 32-year-old singer-actress said. "This is a hard episode for people who are fans of this couple, which I am."

"This is not a great time for them. Things are strained and there's a real disconnect so it will be interesting to see if and how they find their way back together, but this episode really highlights that," Moore added. "That they're probably the furthest apart that we've ever found them."

Because the show jumps around in time, the best visual marker for that has been Ventimiglia's ever-changing facial hair. (In an early episode, Moore was aged up using prosthetics to bring her into the present day.)

"It absolutely helps," the 39-year-old actor said, when asked if it lets him track Jack's journey. "There's one thing with the words on a page but then when you actually have [visual] aids and being like, 'Wow, I have grey hair and I'm wrinkled up and I'm old.' You feel the weight of the world on your shoulders when you have the addition of makeup and hair changing."

Ventimiglia explained why it was important for he and Moore to create a family unit right off the bat.

"Mandy and I talk a bit on set trying to make sure we're all connected and staying connected as a family and knowing that we have these kids," he said. "We all had dinner two weeks ago, and I was randomly sitting at the head of the table and I was like, wow."

"Yeah it was like mom and they were like, 'Thanks mom and dad for organizing dinner,'" Moore recalled.

If fatherhood is in Ventimiglia's future, Moore believes he'll be the perfect dad, in part because of the way he interacts with the mini mes of Rebecca and Jack's adult children, played by Justin Hartley, Chrissy Metz and Sterling K. Brown.

"Milo's really natural. You're gonna be a great dad because you're really good at sort of wrangling everybody," Moore marveled, admitting she's still getting used to playing a mom. "I don't have as much experience so I'm just sort of like thank you. Thank you so much for being good. That was the one note that our director gave us in the second episode."

"He's like, 'Stop saying please and thank you to the children so much. You're mom. You wear the pants. You're the leader,'" she continued. "I'm like, OK, I have to get that ingrained in my brain."

Moore recalled a moment on set when she and Ventimiglia were filming with 2-year-olds . "I'm like I think I'm ready for this. I could definitely do this," Moore adorably admitted.